Internal-combustion engine



May 15, 1945. c. G. CURTIS INTERNAL-COMBUSTION ENGINE 2 Sheets-Sheet 1 Filed Nov. 26, 1943 INVENTOR CHARLES G.CURT,I'S fi'.

07- TTORNEY May 15, 1945. c. e. CURTIS INTERNAL-COMBUSTION ENGINE Filed Nov. 26; 1945 2 Sheets-Sheet 2 INVENTOR. CHARLES G. CURTIS Patented May 15,1945

UNI-TED STATESv PATENT I OFFICE INTERNAL-COMBUSTION ENGINE. Charles G. Curtis, New York, N. -Y. Application November 26, 1943, Serial No. 511,772 r I 4 Claims. :(c1. 123-74) This invention applies to the uniflow type of two-cycle Diesel or gas engine which is providedwith inlet ports at the bottom of the stroke and an exhaust valve or valves at ,the' top of the stroke.

The object I have I in view is to provide a. simple mechanism for furnishingthe necessary scavengingair without adding materially to the moving parts so as to dispense with a separate scavenging blower or compressor, and to provide an efiective and simple means and construction for supplying the scavenging air to the cyclinder without the provision of any header or 'headers. In the drawings, Figure l is a sectional view of the engine frame and one of the cylinders taken at right angles to the crankshaft.

Fig. 2 is a verticalsectional view through the center of the cylinder taken at right angles to the view in Fig. 1. I Fig. 3 is a diagram of valve timing for going ahead.

Fig. 4 is a diagram of valve timing forgoing astern.

Fig. 5 i a modification of the valve timing in Fig. 4. j

' Fig. 6 is a modified form of my engine in which in place of automatic valves controlling the sca'v enging air, I provide valve mechanism driven from a lay-crankshaft.

Fig. '7 is a cross section of the engine, Fig. 1, through the chamber l4. I

In Fig; 1 numeral I represents the cylinder; 11 the inlet ports, and 2 exhaust poppet valve or valves operated in the usual way by a cam l3. Extending over the length of the engine or over several cylinders I provide a longitudinal chamber or compartment M into which-the cylinders! project, so that this compartment feeds directly into the scavenging ports The lower wall of this chamber or compartment consists of a diaphragm or plate l through which the piston rod l6 projects; this piston rod erving to transmit the power from the short piston I! to the auxiliary or-crosshead piston l8.

I make the crossheadin the shape of a round piston which fits closely into the guiding (auxiliary) cylinder l9 which is made a part of, or attached to the engine frame, this piston thus acting not only as a crosshead to take the side thrust of the connecting rod, but as a scavenging air compressor. I provide spaces or passages on each side of the engine which lead into the automatic valves 2| and 22. Valves 2| connect with chambers 23 and valves 22 lead into the scavenging air chamber Hi. When the scavenging piston moves downward it produces a suction in the passages 20 which causes the valves 2| to lift off their seats and air is drawn in through these valves from the air chambers 23. When the piston It! moves upward it compresses the air above it causing the automatic valves 2| to close instantly, and when the pressure has risen to a point a little above the scavenging pressure in the chamber M the valves 22 lift off their seats and the air is forced into the chamber l4. By making the piston I8 slightly largerabout 20 per cent larger in diameter than the main piston H a displacement by the piston I8 is obtained about 44 per cent greater than the displacement of the power piston I1, and allowin for volumetric efficiency I provide a scavenging air ratio of about 125 per cent, which is more than ample to obtain a high scavenging efficiency.

I find that it is not necessary, under most conditions, to provide a packing in the diaphragm l5 where it surrounds the piston rod. A clearance of sufiicient amount canbe provided between the diaphragm and piston to avoid contact, and the quantity of air that will be lost by passing downward from the chamber l4 into the passage 20 will be practically negligible, and has the advantage of blowing back oil which may work up on the piston-rod l6. Several sets of valves can be provided at each side in line with each other, so as to provide ample valve capacity and these valves can readily be reached by covers 25.

I slope the diaphragm l5 from the center downward so that the sludge will run down to the rim of the diaphragm from where it can be drawn off periodically through the tube or drain passage 26. The vertical divisions 2'! in the frame are carried upward to the top of the chamber l4 so as to give the necessary strength and to support thediaphragm i5. As the piston ll moves downward it forces the air into the 'chamber I4 and tends to raisethe pressure in that chamber to some extent. When this piston goes up it tends to produce some suction in chamber Hi. In order to equalize the pressure in the different sections of the chamber under each cylinder so as to maintain a substantially constant scavenging pressure in chamber I4, I provide large openings or passages 21' (Fig. 7 )v through which the jecting portions and can be made smooth on the surface, so that it can readily be kept clean.

In order to avoid taking the strain of the gas pressure on the cylinder head through the bridges between the inlet ports I bolt the cylinder to the compartment I4 making the joint above the level of the ports, the cylinder being held down by a flange 3G with the bolts arranged on the four corners and -of sufiicient strength to take the entire gas strain on the cylinder head. These bolts or studs 3i reaching down through the chamber M, four bolts to each cylinder, are screwed into the frame 23 or carried downward to the base, according to the ordinary ,practice. By making the joint between the cylinder and the engine frame at a point above the scavenging ports there will be no gas pressure at this joint.

By this arrangement I am enabled to take 01f the cylinder and head to get at the piston rings or the valves, and thus avoid the necessity of breaking the gas-tight joint at the top of the cylinder. Instead of having the bolts or studs 3| reach down to the base, theyrmay be threaded into the framework at the level of the automatic inlet valves.

In Fig. 6.. I have shown another form of scavenging air valve, which may be preferable in a high speed engine where the automatic valves are not so well adapted to high speed. In this case, I emp'loy for each cylinder a piston valve 33 reciprocated by a crank 34 on a-crankshaft on which I also mount the injection oil pumps. I time this piston valve so that when the piston is going up the ports'35 are open and the air is forced up intothe chamber 24 through connecting passage 36. As the crosshead piston approaches the top the valve shiftsrapidly so as to close the passage through 36 and open the ports 31 and also ports 35, so as to connect the passage 20 with the chamber 29. As the crosshead piston descends it sucks air in from the chamber 29 through the ports 31 and through the ports 35' into the clearance space 20. By making the piston of sufficient size and the ports of suflicient length, I am. enabled to introduce the air into the clearance 20 on one stroke and to deliver air into the passage 26 on the next stroke with very little loss of pressure, and hence good efficiency.

What is claimed is:

1'. In a uniflow internal combustion engine comprising a plurality of combustion cylinders and pistons and inlet ports in the combustion cylinders at the bottom-of-the-stroke position, a plurality of auxiliary cylinders and pistons, the

latter connected by piston rods with the first named pistons and acting as crossheads; aich amher around and-common to the plurality of cornbustion cylinders and with which each of said combustion cylinders may communicate through said inlet ports when the latter are uncovered by the respective pistons, a diaphragm separat ing said chamber from the auxiliary cylinders, valve mechanism constructed and operating to admit air to the respective auxiliary cylinders when the respective auxiliary pistons move in one direction and to admit to said common chamber compressed air for feeding said inlet ports when the auxiliary pistons move in the opposite direction.

2. In a unifiow internal combustion engine comprising a plurality of combustion cylinders and; pistons and inlet ports in the combustion cylinders at the bottom-of-the-stroke position, a plurality of auxiliary cylinders and pistons, the

latter connected by piston rods with the first named pistons and acting as cross-heads; a chamber around and common to the plurality of combustion cylinders and with which each of the said combustion cylinders may communicate through said inlet ports when the latter are uncovered by the respective pistons, a diaphragm separating said chamber from the auxiliary cylinders, piston valve mechanism constructed and operatingto. admit air to the respective auxiliary cylinderswhenthe respective auxiliary pistons move in one direction and to admit to said common chamber compressed air for feeding said inlet ports when the auxiliary pistons move in the opposite. direction.

3. In a unifiow. internal combustion engine comprising a, plurality of combustion cylinders andpistons and inlet ports in the combustion cylinders at the, bottom-of-the-stroke position, a plurality of auxiliary cylinders and pistons, the latter connected ,by piston-rods with the first named pistonsand acting as cross-heads; a chamber aroundtand common to the plurality of combustion cylinders and with which each of said combustion cylinders may communicate through said inlet ports when the latter are uncovered by the respective pistons, a diaphragm separating said chamber from the auxiliary cylinders, valve mechanism constructed and operating. to, admit air to. the respective auxiliary cylinders when the respective auxiliary pistons movein one direction and to admit to said common chamber compressed air for feeding said inlet pOlfts when the auxiliary pistons move in the opposite direction, said common chamber having bracingpartitions with openings therein through which air may flow to all parts of said common chamber.

4. In a uniflow internal combustion engine according, to claiml, further characterized by said diaphragm having an opening through which said piston rod passes which is of slightly greater diameter than the diameter of the piston' CHARLES G. CURTIS. 

